A novel group of Gastric Antrum Mucosal Proteins that are gastrokines, is characterized. A member of the gastrokine group is designated AMP-18. AMP-18 genomic DNA, and cDNA molecules are sequenced for human and mouse, and the protein sequences are predicted from the nucleotide sequences. The cDNA molecule for pig AMP-18 is sequenced and confirmed by partial sequencing of the natural protein. The AMP-18 protein and active peptides derived from its sequence are cellular growth factors. Surprisingly, peptides capable of inhibiting the effects of the complete protein, are also derived from the AMP-18 protein sequence. Control of mammalian gastro-intestinal tissues growth and repair is facilitated by the use of the protein or peptides, making the protein and the derived peptides candidates for therapies.
Searches for factors affecting the mammalian gastro-intestinal (GI) tract are motivated by need for diagnostic and therapeutic agents. A protein may remain part of the mucin layer, providing mechanical (e.g., lubricant or gel stabilizer) and chemical (e.g against stomach acid, perhaps helping to maintain the mucus pH gradient and/or hydrophobic barrier) protection for the underlying tissues. The trefoil peptide family has been suggested to have such general cytoprotectant roles (see Sands and Podolsky, 1996). Alternatively, a cytokine-like activity could help restore damaged epithelia. A suggestion that the trefoil peptides may act in concert with other factors to maintain and repair the epithelium, further underlines the complexity of interactions that take place in the gastrointestinal tract (Podolsky, 1997). The maintenance of the integrity of the GI epithelium is essential to the continued well-being of a mammal, and wound closing after damage normally occurs very rapidly (Lacy, 1988), followed by proliferation and differentiation soon thereafter to reestablish epithelial integrity (Nusrat et al., 1992). Thus protection and restitution are two critical features of the healthy gastrointestinal tract, and may be important in the relatively harsh extracellular environment of the stomach.
Searches for GI proteins have met with some success. Complementary DNA (cDNA) sequences to messenger RNAs (mRNA) isolated from human and porcine stomach cells were described in the University of Chicago Ph.D. thesis “Characterization of a novel messenger RNA and immunochemical detection of its protein from porcine gastric mucosa,” December 1987, by one of the present inventors working with the other inventors. However, there were several cDNA sequencing errors that led to significant amino acid changes from the AMP-18 protein disclosed herein. The protein itself was isolated and purified only as an aspect of the present invention, and functional analyses were performed to determine utility. Nucleic acid sequences were sought.